Roof-mounted air conditioning systems for passenger busses, railway cars and the like have been devised either in which the condensor and evaporator sections are in a common housing or are in separate housings so as to be more readily conformable for mounting at different locations on the roof or exterior of the vehicle. For example, reference is made to my U.S. Pat. No. 4,679,616 for a modular arrangement of evaporator and condensor units on the roof of a vehicle. Moreover, there are applications where it becomes desirable to be able to incorporate the compressor for the air conditioning system into the roof of the vehicle and thereby avoid lengthy connecting lines between the compressor and the rest of the air conditioning system.
In the past, it has been proposed to incorporate the compressor into a roof-mounted air conditioning system and, for example, U.S. Pat. No. 4,905,478 illustrates several variations on this approach. However, there is generally lacking in the prior art a recognition of the problems associated with mounting of the compressor on the roof and particularly when installed in direct association with the condensor section. Thus, it is important that the compressor be mounted in proper load-balanced relation to the roof and in such a way as not to appreciably increase wind resistance. Further, it is important that the compressor section be cooled but not to such an extent as to draw in excessive amounts of moisture which will have a deleterious effect on the operation of the compressor motor; and to carry out cooling without the necessity of additional cooling fans or other auxiliary cooling devices.